The Laboratory Animal Facility (LAP) is responsible for the procurement, husbandry, breeding and monitoring of all vertebrate animals used at the Fox Chase Cancer Center (FCCC). The Facility is currently used by 42 peer-reviewed, funded investigators from 11 research Programs representing all three Divisions of the Center. Ninety-six percent (96%) of LAP use supports peer-review research. The staff of the Facility provides animal related technical expertise to, and collaborates with, the various research laboratories using the Facility. The Facility also maintains six genetically defined mouse strains, which are unique to this Center. The Facilities are fully accredited by the Association for the Assessment and Accreditation of Laboratory Animal Care, International (AAALAC) and are designated as registered research Facilities by the U.S. Department of Agriculture. The Research Animal Facility contains 14,204 sq. ft. of animal space distributed over four floors. Six separate areas house: 1) research rodents on projects (including transgenic and immunodeficient mice) in micro isolators;2) a specific pathogen-free (SPF) breeding barrier for crossing and manipulating special genetic strains of mice for research investigators;3) an adjoining SPF barrier building used by the LAP for breeding nucleus colonies of foundation mouse stocks and inbred strains;4) an area on the ground floor of the NMR building used for isolation and rederivation of newly arrived rodents at the Center;5) conventional housing for research mice, rats, rabbits and Xenopus laevis;and 6) an area on the first floor for housing domestic and wild-caught woodchucks and Pekin Ducks. The number of research mouse cages has increased more than two-fold over the past five years and an average annual increase of 18% is projected for the future. The Facility is currently filled to capacity. The Center has added three high density ventilated rodent racks in 2003 and has committed to do the same each year in the future;the addition of these high-density racks must be accelerated to meet expected research growth. All breeding animals and all transgenic, immunodeficient, and rederived animals are now housed in microisolator cages, and these areas have all remained free of murine pathogens for the past three years. Technical services supplied by the animal care and support staff have increased almost three-fold (287%) and are expected to continue to expand in the future.